Specific Heat of Co_2TiO_4 and its Anomaly Associated with Magnetic Transition

概要

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The specific of a ferrimagnet Co_2TiO_4 which has a spinel structure was measured between 2°K and room temperature. An anomalous heat due to a magnetic transition was observed. The Curie temperature is found to be 49.0°K. The total entropy of the transition is approximately Rln8 which suggests that the degeneracies of ground states of Co_<2+> ions in tetrahedral and octahedral sites are fourfold and twofold respectively. The Debye temperature is 560°K. The observed magnetic specific heat below about 30°K shows the modified T^3/2 dependence which is predicted from the spin wave theory taking into account the anisotropy energy, except at very low temperature. The effective anisotropy field, 2K/M_S, is 4.8xl0^4Oe. The absolute magnitude of the exchange Interaction of the spin, 3/2, of a Co^<2+> jon in a tetrahedral site with the fictitious spin, l/2, of a Co^<2+> jon in an octahedral site, J_<ΔB'> is evaluated to be 3.23k_B.
社団法人日本物理学会の論文
1965-04-05